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Check authorized_keys permissions as the user

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This is necessary on NFS with squash root.
Based on work from Chris Dragan
This commit also tidies some trailing whitespace.

Fixes github pull #107
This commit is contained in:
Matt Johnston 2022-03-30 12:56:09 +08:00
parent 6f793d42d0
commit 2f68f6693f
1 changed files with 38 additions and 40 deletions
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78
svr-authpubkey.c
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@ -1,19 +1,19 @@
/*
* Dropbear - a SSH2 server
*
*
* Copyright (c) 2002,2003 Matt Johnston
* All rights reserved.
*
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
@ -22,11 +22,11 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
/*
* This file incorporates work covered by the following copyright and
* This file incorporates work covered by the following copyright and
* permission notice:
*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
@ -35,7 +35,7 @@
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
@ -48,7 +48,7 @@
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* This copyright and permission notice applies to the code parsing public keys
* options string which can also be found in OpenSSH auth2-pubkey.c file
* options string which can also be found in OpenSSH auth2-pubkey.c file
* (user_key_allowed2). It has been adapted to work with buffers.
*
*/
@ -108,7 +108,7 @@ void svr_auth_pubkey(int valid_user) {
if (!valid_user) {
/* Return failure once we have read the contents of the packet
required to validate a public key.
required to validate a public key.
Avoids blind user enumeration though it isn't possible to prevent
testing for user existence if the public key is known */
send_msg_userauth_failure(0, 0);
@ -130,9 +130,9 @@ void svr_auth_pubkey(int valid_user) {
if (svr_ses.plugin_instance->checkpubkey(
svr_ses.plugin_instance,
&ses.plugin_session,
keyalgo,
keyalgolen,
keyblob,
keyalgo,
keyalgolen,
keyblob,
keybloblen,
ses.authstate.username) == DROPBEAR_SUCCESS) {
/* Success */
@ -141,7 +141,7 @@ void svr_auth_pubkey(int valid_user) {
/* Options provided? */
options_buf = ses.plugin_session->get_options(ses.plugin_session);
if (options_buf) {
struct buf temp_buf = {
struct buf temp_buf = {
.data = (unsigned char *)options_buf,
.len = strlen(options_buf),
.pos = 0,
@ -174,7 +174,7 @@ void svr_auth_pubkey(int valid_user) {
}
/* now we can actually verify the signature */
/* get the key */
key = new_sign_key();
if (buf_get_pub_key(ses.payload, key, &keytype) == DROPBEAR_FAILURE) {
@ -191,7 +191,7 @@ void svr_auth_pubkey(int valid_user) {
/* The entire contents of the payload prior. */
buf_setpos(ses.payload, ses.payload_beginning);
buf_putbytes(signbuf,
buf_putbytes(signbuf,
buf_getptr(ses.payload, sign_payload_length),
sign_payload_length);
buf_incrpos(ses.payload, sign_payload_length);
@ -213,7 +213,6 @@ void svr_auth_pubkey(int valid_user) {
svr_ses.plugin_instance->auth_success(ses.plugin_session);
}
#endif
} else {
dropbear_log(LOG_WARNING,
"Pubkey auth bad signature for '%s' with key %s from %s",
@ -290,7 +289,7 @@ static int checkpubkey_line(buffer* line, int line_num, const char* filename,
unsigned char *options_start = NULL;
int options_len = 0;
int escape, quoted;
/* skip over any comments or leading whitespace */
while (line->pos < line->len) {
const char c = buf_getbyte(line);
@ -313,7 +312,7 @@ static int checkpubkey_line(buffer* line, int line_num, const char* filename,
quoted = 0;
escape = 0;
options_len = 0;
/* figure out where the options are */
while (line->pos < line->len) {
const char c = buf_getbyte(line);
@ -338,7 +337,7 @@ static int checkpubkey_line(buffer* line, int line_num, const char* filename,
}
}
buf_incrpos(line, algolen);
/* check for space (' ') character */
if (buf_getbyte(line) != ' ') {
TRACE(("checkpubkey_line: space character expected, isn't there"))
@ -427,23 +426,8 @@ static int checkpubkey(const char* keyalgo, unsigned int keyalgolen,
TRACE(("enter checkpubkey"))
/* check file permissions, also whether file exists */
if (checkpubkeyperms() == DROPBEAR_FAILURE) {
TRACE(("bad authorized_keys permissions, or file doesn't exist"))
goto out;
}
/* we don't need to check pw and pw_dir for validity, since
* its been done in checkpubkeyperms. */
len = strlen(ses.authstate.pw_dir);
/* allocate max required pathname storage,
* = path + "/.ssh/authorized_keys" + '\0' = pathlen + 22 */
filename = m_malloc(len + 22);
snprintf(filename, len + 22, "%s/.ssh/authorized_keys",
ses.authstate.pw_dir);
#if DROPBEAR_SVR_MULTIUSER
/* open the file as the authenticating user. */
/* access the file as the authenticating user. */
origuid = getuid();
origgid = getgid();
if ((setegid(ses.authstate.pw_gid)) < 0 ||
@ -451,9 +435,24 @@ static int checkpubkey(const char* keyalgo, unsigned int keyalgolen,
dropbear_exit("Failed to set euid");
}
#endif
/* check file permissions, also whether file exists */
if (checkpubkeyperms() == DROPBEAR_FAILURE) {
TRACE(("bad authorized_keys permissions, or file doesn't exist"))
} else {
/* we don't need to check pw and pw_dir for validity, since
* its been done in checkpubkeyperms. */
len = strlen(ses.authstate.pw_dir);
/* allocate max required pathname storage,
* = path + "/.ssh/authorized_keys" + '\0' = pathlen + 22 */
filename = m_malloc(len + 22);
snprintf(filename, len + 22, "%s/.ssh/authorized_keys",
ses.authstate.pw_dir);
authfile = fopen(filename, "r");
authfile = fopen(filename, "r");
if (!authfile) {
TRACE(("checkpubkey: failed opening %s: %s", filename, strerror(errno)))
}
}
#if DROPBEAR_SVR_MULTIUSER
if ((seteuid(origuid)) < 0 ||
(setegid(origgid)) < 0) {
@ -485,7 +484,6 @@ static int checkpubkey(const char* keyalgo, unsigned int keyalgolen,
}
/* We continue to the next line otherwise */
} while (1);
out:
@ -508,7 +506,7 @@ out:
* g-w, o-w */
static int checkpubkeyperms() {
char* filename = NULL;
char* filename = NULL;
int ret = DROPBEAR_FAILURE;
unsigned int len;
@ -547,7 +545,7 @@ static int checkpubkeyperms() {
/* file looks ok, return success */
ret = DROPBEAR_SUCCESS;
out:
m_free(filename);